1. Field of the Invention
The present invention relates generally to an apparatus for controllably blending gases. More particularly the invention concerns an apparatus for blending gases such as nitrogen and carbon dioxide for use in connection with beverage dispensing systems of the character wherein beverage contained in a bulk container is controllably dispensed therefrom by admission of the gas mixture under pressure to the container.
2. Discussion of the Prior Art
The use of carbon dioxide gas in the dispensing of beverages such as beer, ale or stout is well known. However, it has been found that for certain applications the use of a mixture of carbon dioxide gas and a second gas, such as nitrogen, provides certain advantages. For example, the use of such a mixture alleviates excessive carbonization of the beverage being dispensed and, when used in dispensing beer, advantageously achieves a stable and creamy head on the beer.
While the advantages of using a gaseous mixture of nitrogen and carbon dioxide in dispensing beer has been known for some time, substantial difficulties have been encountered in designing an accurate, reliable and inexpensive device for mixing the nitrogen and carbon dioxide in the correct proportions. One of the most successful devices to accomplish such mixing is disclosed in U.S. Pat. No. 4,874,116 issued to the present inventors. An improvement of the device described in the aforementioned patent is disclosed in U.S. Pat. No. 4,928,850 also issued to the inventors named herein. As will become apparent from the descriptions which follow, the device of the present invention comprises yet a further improvement upon the device described in U.S. Pat. No. 4,928,8550.
Due to the novel design of the apparatus of the present invention, the high-flow element of the device is isolated from the gas flow path when the device is being operated in the low-flow mode. This eliminates the undesirable and time consuming necessity to continuously adjust the balance of the gases being mixed as temperature and shock environments change during operation.